Many network communication systems often need to provide Ethernet interface and USB Device interface that allow external electronics device to communicate with it using either interface of choice. Typically, the Ethernet interface is applied for interconnecting to an Ethernet network, a PC, a laptop computer or another network communication system through a regular Ethernet cable while the USB Device interface (as a USB Communication Class device) is applied for interconnecting to a USB Host built-in to a PC, a laptop computer or any embedded system through a regular USB cable.
There are some common system design approaches with related problems for above mentioned network communication systems that need the support of Ethernet and USB interface.
The first problem deals with the Network Communication System Featuring Ethernet Interface Only.
FIG. 4 illustrates a typical network communication system supporting Ethernet interface for interconnecting to an Ethernet network, a PC, a laptop computer or another network communication system through a regular Ethernet cable. Typically, an Ethernet PHY chip 402 is used for providing physical layer function for the Ethernet MAC of the Network Microcontroller 401.
The second problem deals with the Network Communication System Featuring USB Interface Only.
FIG. 5 illustrates a typical network communication system supporting USB interface for interconnecting to a USB Host 505 built-in to a PC, a laptop computer or any embedded system through a regular USB cable. Typically, a USB-to-Ethernet Controller chip 501 is used for bridging between the external USB Host 505 and the Ethernet MAC 506 of Network Microcontroller. Usually the Ethernet MACs in both the Network Microcontroller and the USB-to-Ethernet Controller only support the pure MAC function, so to interconnect two Ethernet MAC through the MII interface; a special MAC-to-MAC connection circuitry must be used. FIG. 14 show typical examples for MAC-to-MAC connection using MII interface between two Ethernet MAC devices.
FIG. 13 illustrates typical MAC-to-PHY connection using MII interface between two Ethernet MAC device and Ethernet PHY device.
Note that FIG. 5 does not apply to the case where the USB Device PHY interface already been integrated into the Network Microcontroller, in which case, it is not related to the proposed invention (not a USB Communication Class device).
The third problem deals with the Network Communication System Featuring Ethernet and USB Interfaces.
FIG. 6 illustrates a typical network communication system supporting Ethernet and USB interfaces. Usually an Ethernet PHY chip 603 and a USB-to-Ethernet controller chip 602 are used and they are sharing the same MII interface of the Ethernet MAC of the Network Microcontroller 601. To support such interconnection, there are following restrictions:
Both the Ethernet PHY chip and the USB-to-Ethernet Controller chip must support tri-state mode on its MII interface. In other words, when Ethernet interface is in use, the USB-to-Ethernet Controller chip must be set to tri-state on its MII interface in order not to interfere with the Ethernet PHY chip, or vice-versa. If either one's MII interface is not capable of entering tri-state mode, some external glue logics such as bus transceiver chip would be required.
Usually the Ethernet MAC of the USB-to-Ethernet Controller chip is a pure MAC device that does not allow it to glue less interconnect with the Network Microcontroller directly, not to mention having it share with the Ethernet PHY chip through the same MII interface of the Network Microcontroller. Again the special MAC-to-MAC connection circuitry must be used.
If the network communication system supports automatic detection and selection for the use of Ethernet interface and USB interface, some external glue logics would be required. The automatic detection and selection means, for example, if user plugs in Ethernet cable, the Ethernet PHY chip should be enabled automatically to be the active path inter networking with the Network Microcontroller, or if USB cable is plugged in, the USB-to-Ethernet Controller chip should be enabled as active path instead. The designer of the network communication system can define his own rule of which one takes the priority to be the active path when the Ethernet and the USB cable are both plugged in by user at the same time.
Usually the Ethernet MAC of the USB-to-Ethernet Controller is a pure MAC function, which means, it doesn't allow the Ethernet MAC of Network Microcontroller to control/configure its operation mode or check its operation status via the commonly used Station Management Interface (MDC and MDIO lines) as defined in IEEE 802.3u standard. The Ethernet MAC of the USB-to-Ethernet Controller, also as a Station Management Interface master, actually expects to control/configure/check the external device. Therefore, some external glue logics would be required to allow the Network Microcontroller to select the active path based on user's cable connection action. Note that the Ethernet PHY chip usually can be configured through its Station Management Interface (MDC and MDIO lines).